KENNEDY SPACE CENTER, FLA. - In the Payload Hazardous Servicing Facility, elements of one of the Mars Exploration Rovers (MER) come together. In the foreground is a lander. In the background are an aeroshell, with the heat shield on top, and cruise stage below. The two rovers, MER-1 and MER-2 , aeroshells and landers will undergo a full mission simulation while at KSC. All flight elements will then be integrated. After spin balance testing, each spacecraft will be mated to a solid propellant upper stage booster that will propel it out of Earth orbit. The rovers will serve as robotic geologists to seek answers about the evolution of Mars, particularly for a history of water. The rovers will be identical to each other, but will land at different regions of Mars. Launch of the MER-1 is scheduled for May 30. MER-2 will follow June 25.